Variable condenser system



Dec. 19 1933. LANGLEY 1,939,856

VARIABLE CONDENSER SYSTEM Filed Feb. 4, 1929 A TTORNE Y.

Patented Dec. 19, 1933 UNITED STATES PATENT OFFICE VARIABLE CONDENSER SYSTEM Application February 4, 1929. Serial No. 337,473

Claims.

My invention relates to the provision of a suitable gang condenser system for radio receivers. In the modern radio receiver it is usual to tune two or more radio frequency circuits by 5 means of a series of condensers, one for each circuit, said condensers having a common operating shaft, on which all of the rotors are mounted.

Because of the fact that antennae used with radio receivers are usually attached by the users of the sets, the manufacturer of the receiver cannot so arrangehis receiver that the circuits directly affected by the antenna will be alike in all installations. Accordingly, in gang condenser types of radio receivers, it is customary to use an untuned circuit with the grid of the first vacuum tube. When this is done the first tube does not produce the full amplification of which it is capable, and the fact that the antenna is thus left untuned, materially decreases the selectivity of the set.

The object of the present invention is to provide for tuning of the antenna by the use of a gang condenser which has a structure permitting of an independent movement of the condenser in the circuit of the grid of the first tube.

I am aware that gang condenser systems have been produced which are so arranged as to permit of separate adjustment of selected condensers, but do not understand that this mechanical expedient has been employed for the outlined purpose. Furthermore, I have produced a simple, and novel mechanical structure for accomplishing my purpose which is simple to construct and effective in operation.

In the drawing, in which I have illustrated my invention in two embodiments, among those that I have evolved to accomplish my purpose Figure 1 is a perspective view of the condenser system.

Figure 2 is a wiring diagram showing the position and operation of the independently adjustable condenser element of the gang.

Figure 3 is a detail side elevation showing one of the frictional drive methods employed by me.

Figure 4 is a side elevation taken of the same parts as Figure 3 from the opposite side.

Figure 5 is a section taken centrally through the parts shown in Figures 3 and 4.

Referring first to the wiring diagram, I have illustrated diagrammatically an antenna 1, which is coupled to the grid circuit 2 of the first vacuum tube 3. There are illustrated two additional stages of radio frequency amplification having grid circuits 4 and 5. The condensers 6 and '7 are in the grid circuits 4 and 5, and the condenser 8 is in the grid circuit 2. There may be as many radio frequency amplification circuits as are desired.

The several variable condensers are normally operated by a common element, which will serve for the preliminary tuning of the receiver for some given signal. When the station has been brought in, the first condenser 8 is additionally moved or varied without moving the other condensers. This brings the antenna and the first 6 grid circuit to full resonance with the signal and tunes out other overlapping signals, as well as increasing the amplification of the signal itself.

As a preferred method of accomplishing this object, I have shown in Figure 1 a suitable arrangement. In this arrangement there is shown a series of stator plate assemblies 9, at one side of the control drum, and a single stator plate assembly 10 at the other side. There are two shafts employed, the shaft 11, which has supporting bearings at 11a and 11b, and the shaft 12 which has supporting bearings at 12a and 12b. The rotor plates 13 for the several stator assemblies 9 are mounted on the shaft 11. The rotor plates 14 for the stator 10 are mounted on the shaft 12.

Secured fast on the shaft 11 is a large drum 14, the periphery of which is traversed by an operating belt 15. This belt is passed around an idler l6 and thence around an operating spindle 17. The spindle 17 is driven by means of a finger piece or dial 18, and a suitable brake 19 may be applied to the spindle.

Secured fast on the shaft 12 is a drum 20 which has a driving belt 21, passing around a similar idler 22 and operating dial and spindle 23.

The drum 14 is hollow, and the drum 20 may be formed in a conical shape, so as to present a flange 20a, which will enter the hollow of the drum 14.

In the form shown in Figure 1 I have illustrated a series of spring strips 24 bent up into a star shape, and thrust between the flange of the inner drum, and the interior of the periphery of the outer drum. This arrangement provides for a frictional drive of the inner drum by the outer drum.

As an adjustable frictional means (Figs. 3, 4 and 5) I may equip the inside of the outer drum with spring fingers 25, which bear against the flange of the inner drum. Adjusting screws 26 in the outer drum bear against these springs, and thus adjust the frictional contact.

The arrangement is such that when the operator revolves the main finger piece or dial 18,

he will move all rotor plates through a like arc. When he moves the spindle 23, the friction between the two drums will not be enough to overcome the effect of the brake on the operating spindle of the main drum, and the rotor plates 14 of the left hand condenser will be the only ones which are moved.

In order to provide for travel of the driving belts on the spindles 17 and 23, and thus prevent a piling up and binding of them, the inner ends 17a and 23a of the two spindles are threaded, and engage in threaded bearings (not shown). This structure permits the spindle drums to travel as the belts travel on the spindle drums, thus permitting a free operation at all times.

To a certain degree it will be desirable upon the first installation of the receiver to make an adjustment of the inner drum, and hence of the position of the rotor assembly for the first grid circuit, by slipping the drum under the belt. This will constitute the main compensation for the antenna, and future changes while the set is being used will not be great. Local signals will not ordinarily require anything but the preliminary arrangement noted. It will, however, be necessary for the best reception in the set for the antenna circuit to be given a close tuning, by a separate operation, as above outlined, each time a signal is brought in. This is because the characteristics of the antenna circuit are not the same as that of the circuits in the vacuum tube circuits, and cannot be accurately tuned by an equal change in condenser capacity.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is:-- v

1. In a variable adjustment device a series of rotors, a shaft constituting a common support of the rotors, another shaft with at least one further rotor thereon, axially aligned and frictionally connected to the common rotor supporting shaft first noted, a brake sufficient to prevent rotation of the common shaft when the other shaft is rotated, and means for driving the common shaft and the other shaft comprising drums on said shafts and belts for driving said drums, control finger pieces and drums rotated thereby for driving said belts.

2. A drive for shafts which are axially arranged which comprises a large drum on one shaft, a drum on the other shaft having an extension lying within the large drum, frictional engaging means within the large drum to engage said extension, and belt drives for the two drums, and a brake for one drive to keep it from moving when the other drive is moved.

3. In a variable adjustment device, axially alined rotatable members in frictional contact to rotate together or to slip relatively to each other, rotatable manipulating devices on axes transverse to the axis of said members, belts, each frictionally engaging around one of said members and a respective manipulating device, and a brake frictionally engaging one of said devices and permitting manipulation of said one of said devices to drive both members and the other device, but said brake and the belt conmeeting said one device with its respective rotatable member having more effective frictional contact than that between said rotatable members, whereby the other device may drive only the one member to which it is belted.

4. In an adjustment device, a drum and an idler on parallel axes, a second drum on an axis transverse to said axes, between the idler and the first drum, a belt stretched around the first drum and the idler and having one strand passing in a loop around the second drum, and means actuated incident to rotation of the second drum to move the drum axially, to avoid displacing engagement of one part of said loop with another.

5. In a variable adjustment device, axially alined rotatable telescoping members with radially spaced concentric surfaces, spring means between said surfaces frictionally connecting the members to rotate together or to slip relatively to each other, rotatable manipulating devices, means operatively connecting said devices to the respective members, the means connecting one member and its manipulating device rendering said member rotatable by and capable of rotating its manipulating device, and the means connecting the other member and its manipulating device rendering said other member rotatable by its manipulating device, but being capable of slippage, and means effective to hold the latter manipulating device with friction. in excess of slippage of the latter connecting means, whereby said other member is incapable of rotating its manipulating device.

RALPH H. LANGLEY. 

